This relates to a ventilator and, more particularly, to one that is normally mounted at the end of a conduit to enhance flow out of the conduit.
It is known to provide ventilators at the upper ends of conduits in order to enhance the vertical flow through them.
The simplest type of such a ventilator is a so-called static ventilator which is so constituted as to employ normally present air currents to enhance the draft from the upwardly open conduit mouth. This can most simply be done by mounting a flat plate above the upper mouth of the conduit so that as air passes horizontally between the plate and the conduit mouth gases are sucked from the conduit by the Pitot effect.
Dynamic ventilators are known, such as described in my U.S. Pat No. 4,200,035. These arrangements have a fan provided at the upper end of the conduit mouth and serving physically to suck air out of the conduit. Such arrangements are extremely effective, yet have the disadvantage that the air rising out of the conduit passes over the blades of the fan and normally also over the drive motor for the fan, thereby heating it considerably.
My U.S. Pat. No. 4,342,258, which is incorporated herein by reference, describes an improved device for the ventilation of rooms and the draft of chimneys. In such device, a disk is mounted above the open end of the duct and an impeller and motor are mounted above the disk so as to create a descending vertical air current to embrace the draft from the duct. Static ventilation is provided by the effect of the low pressure created in the ventilation duct or chimney by an air current that envelopes a toroidal bulb placed at the mouth of the duct. Dynamic ventilation is provided by the descending vertical air current. This arrangement has the additional advantage that the descending vertical air current cools the motor, thus protecting it from heating that would have harmed its service life.